Most ministers in Cabinet earn nearly $300,000 - around $250,000 more than the average NZ salary of around $50,000. A backbench MP with no additional responsibilities earns $160,000, while the base primary teacher salary starts at $48,000.

ACT leader David Seymour thinks the amount being paid is "about right", but wants to restrict the number of high-paid Ministers to 20.

"There are plenty of MPs who are earning more in Parliament than they would in the private sector," Mr Seymour told Newshub.

"MPs get used to the baubles and never leave. Look at Winston Peters - how would he fare in the real world?"

He says taking a pay cut shouldn't dissuade people who genuinely want to serve the public from standing for office.

So how should their MP's pay be determined?

Currently, salaries are set by the independent Remuneration Authority, and increases are pegged to increases in the wider public service. Average salary increases across the private sector, which have been lower, have no direct influence.

Dr Eric Crampton, the chief economist at libertarian think tank The New Zealand Initiative, says this can create the "perverse incentive" of linking pay to high public sector salaries - encouraging the Government to give pay rises to teachers, doctors and nurses.

"MPs should be rewarded when they raise the living standards of ordinary Kiwis. That's why it's important to link our pay to increases in productivity and wages in the real economy," Mr Seymour says.

"An interesting option might be to simply bulk-fund political parties the equivalent of total current spending on MPs, staffers and other resources: then the parties could decide who deserved higher and lower pay - how much is used for MP's pay, and how much is used for support staff," Mr Ascroft told Newshub.

"Another option would be to simply link the wages of MPs to the median wage, in order to encourage good economic management."

Big private sector pay-outs for MPs

After they leave Parliament, New Zealand's MPs find a variety of roles and sinecures. Some move into executive and board positions, others go into highly paid lobbying - often in the same area they oversaw as ministers.

"Most MPs land on their feet when their former colleagues give them cushy board roles or ambassadorships," Mr Seymour says.

"Both National and Labour have made a habit of handing out jobs for the boys and girls."

Sir John Key has been appointed to the board of directors of Air New Zealand, as well as chairman of ANZ Bank New Zealand.

Former Green Party MP Russel Norman is now executive director of Greenpeace, National MP Katherine Rich is the CEO of the New Zealand Food & Grocery Council and former Minister of Health Dr Jonathan Coleman left to run the private sector health company Acurity.

"Finding work as a former-MP is much easier than most people making a difficult career transition," Mr Ascroft told Newshub.

"There are an array of ambassadorships and boards that are regularly filled by previous MPs, while lobbying firms and companies seeking subsidies always find it useful to have experienced politicians stalking the streets of Wellington in search of Government largesse."

Overseas, other democracies have 'cooling off periods' which prevent MPs from working in the private sector, especially in the industries they used to regulate.